add miri-test-libstd support to libstd
- The first commit mirrors what we already have in liballoc.
- The second commit adds some regression tests that only really make sense to be run in Miri, since they rely on Miri's extra checks to detect anything.
- The third commit makes the MPSC tests work in reasonable time in Miri by reducing iteration counts.
- The fourth commit silences some warnings due to code being disabled with `cfg(miri)`
Windows: Load synch functions together
Attempt to load all the required sync functions and fail if any one of them fails.
This fixes a FIXME by going back to optional loading of `WakeByAddressSingle`.
Also reintroduces a macro for optional loading of functions but keeps it separate from the fallback macro rather than having that do two different jobs.
r? `@thomcc`
Fix trailing space showing up in example
The current text is rendered as: U+005B ..= U+0060 ``[ \ ] ^ _ ` ``, or (**note the final space!**)
This patch changes that to render as: U+005B ..= U+0060 `` [ \ ] ^ _ ` ``, or (**note no final space!**)
The reason for that, is that CommonMark has a solution for starting or ending inline code with a backtick/grave accent: padding both sides with a space, makes that padding disappear.
Expose `Utf8Lossy` as `Utf8Chunks`
This PR changes the feature for `Utf8Lossy` from `str_internals` to `utf8_lossy` and improves the API. This is done to eventually expose the API as stable.
Proposal: rust-lang/libs-team#54
Tracking Issue: #99543
Avoid zeroing a 1kb stack buffer on every call to `std::sys::windows::fill_utf16_buf`
I've also tried to be slightly more careful about integer overflows, although in practice this is likely still not handled ideally.
r? `@ChrisDenton`
Refactor iteration logic in the `Flatten` and `FlatMap` iterators
The `Flatten` and `FlatMap` iterators both delegate to `FlattenCompat`:
```rust
struct FlattenCompat<I, U> {
iter: Fuse<I>,
frontiter: Option<U>,
backiter: Option<U>,
}
```
Every individual iterator method that `FlattenCompat` implements needs to carefully manage this state, checking whether the `frontiter` and `backiter` are present, and storing the current iterator appropriately if iteration is aborted. This has led to methods such as `next`, `advance_by`, and `try_fold` all having similar code for managing the iterator's state.
I have extracted this common logic of iterating the inner iterators with the option to exit early into a `iter_try_fold` method:
```rust
impl<I, U> FlattenCompat<I, U>
where
I: Iterator<Item: IntoIterator<IntoIter = U>>,
{
fn iter_try_fold<Acc, Fold, R>(&mut self, acc: Acc, fold: Fold) -> R
where
Fold: FnMut(Acc, &mut U) -> R,
R: Try<Output = Acc>,
{ ... }
}
```
It passes each of the inner iterators to the given function as long as it keep succeeding. It takes care of managing `FlattenCompat`'s state, so that the actual `Iterator` methods don't need to. The resulting code that makes use of this abstraction is much more straightforward:
```rust
fn next(&mut self) -> Option<U::Item> {
#[inline]
fn next<U: Iterator>((): (), iter: &mut U) -> ControlFlow<U::Item> {
match iter.next() {
None => ControlFlow::CONTINUE,
Some(x) => ControlFlow::Break(x),
}
}
self.iter_try_fold((), next).break_value()
}
```
Note that despite being implemented in terms of `iter_try_fold`, `next` is still able to benefit from `U`'s `next` method. It therefore does not take the performance hit that implementing `next` directly in terms of `Self::try_fold` causes (in some benchmarks).
This PR also adds `iter_try_rfold` which captures the shared logic of `try_rfold` and `advance_back_by`, as well as `iter_fold` and `iter_rfold` for folding without early exits (used by `fold`, `rfold`, `count`, and `last`).
Benchmark results:
```
before after
bench_flat_map_sum 423,255 ns/iter 414,338 ns/iter
bench_flat_map_ref_sum 1,942,139 ns/iter 2,216,643 ns/iter
bench_flat_map_chain_sum 1,616,840 ns/iter 1,246,445 ns/iter
bench_flat_map_chain_ref_sum 4,348,110 ns/iter 3,574,775 ns/iter
bench_flat_map_chain_option_sum 780,037 ns/iter 780,679 ns/iter
bench_flat_map_chain_option_ref_sum 2,056,458 ns/iter 834,932 ns/iter
```
I added the last two benchmarks specifically to demonstrate an extreme case where `FlatMap::next` can benefit from custom internal iteration of the outer iterator, so take it with a grain of salt. We should probably do a perf run to see if the changes to `next` are worth it in practice.
Don't derive `PartialEq::ne`.
Currently we skip deriving `PartialEq::ne` for C-like (fieldless) enums
and empty structs, thus reyling on the default `ne`. This behaviour is
unnecessarily conservative, because the `PartialEq` docs say this:
> Implementations must ensure that eq and ne are consistent with each other:
>
> `a != b` if and only if `!(a == b)` (ensured by the default
> implementation).
This means that the default implementation (`!(a == b)`) is always good
enough. So this commit changes things such that `ne` is never derived.
The motivation for this change is that not deriving `ne` reduces compile
times and binary sizes.
Observable behaviour may change if a user has defined a type `A` with an
inconsistent `PartialEq` and then defines a type `B` that contains an
`A` and also derives `PartialEq`. Such code is already buggy and
preserving bug-for-bug compatibility isn't necessary.
Two side-effects of the change:
- There is only one error message produced for types where `PartialEq`
cannot be derived, instead of two.
- For coverage reports, some warnings about generated `ne` methods not
being executed have disappeared.
Both side-effects seem fine, and possibly preferable.
Attempt to load all the required sync functions and fail if any one of them fails.
This reintroduces a macro for optional loading of functions but keeps it separate from the fallback macro rather than having that do two different jobs.
unwind: don't build dependency when building for Miri
This is basically re-submitting https://github.com/rust-lang/rust/pull/94813.
In that PR there was a suggestion to instead have bootstrap set a `RUST_CHECK` env var and use that rather than doing something Miri-specific. However, such an env var would mean that when switching between `./x.py check` and `./x.py build`, the build script gets re-run each time, which doesn't seem good. So I think for now checking for Miri probably causes fewer problems.
r? ````@Mark-Simulacrum````
Update the minimum external LLVM to 13
With this change, we'll have stable support for LLVM 13 through 15 (pending release).
For reference, the previous increase to LLVM 12 was #90175.
r? `@nagisa`
The current text is rendered as: U+005B ..= U+0060 ``[ \ ] ^ _ ` ``, or.
This patch changes that to render as: U+005B ..= U+0060 `` [ \ ] ^ _ ` ``, or
The reason for that, is that CommonMark has a solution for starting or ending inline code with a backtick/grave accent: padding both sides with a space, makes that padding disappear.
fix(iter::skip): Optimize `next` and `nth` implementations of `Skip`
This avoids calling nth/next or nth/nth to first skip elements and then get the next one (unless necessary due to usize overflow).
Fix HorizonOS regression in FileTimes
The changes in #98246 caused a regression for multiple Newlib-based systems. This is just a fix including HorizonOS to the list of targets which require a workaround.
``@AzureMarker`` ``@ian-h-chamberlain``
r? ``@nagisa``
Add `Iterator::array_chunks` (take N+1)
A revival of https://github.com/rust-lang/rust/pull/92393.
r? `@Mark-Simulacrum`
cc `@rossmacarthur` `@scottmcm` `@the8472`
I've tried to address most of the review comments on the previous attempt. The only thing I didn't address is `try_fold` implementation, I've left the "custom" one for now, not sure what exactly should it use.
